The present invention relates generally to a mechanically driven hay harvesting implement having a centrally pivoted draft tongue. In particular, this invention relates to a steering mechanism on the mechanical drive line for pivotally rotating a rotatable gearbox in response to the pivotal movement of the tongue.
Pull-type harvesting implements have been utilized for various harvesting operations for many years. These harvesting implements, supported primarily by ground engaging wheels, are made in a variety of configurations, but normally include components supported on a frame. One of these components is a pivotal draft member, commonly called a drawbar or a draft tongue. For convenience, any draft member discussed in the following description will be referred to as a draft tongue.
In pull-type harvesters, the tongue extends forwardly of the frame for attachment to a prime mover, such as a tractor, which pulls the implement and provides operative power for various harvesting components supported by the main frame. For example, if the implement is a mower-conditioner, cutting and conditioning components mounted on the frame require operative power, which are provided mechanically and/or hydraulically by the tractor. Hydraulic drive systems are costly and have been fraught with operational problems, not the least of which is power limitations, particularly when large implements are involved. Thus, in light of such problems, implement designers have turned to the use of a mechanical drive line between the tractor and the harvester.
U.S. Pat. No. 4,187,664, issued Feb. 12, 1980 in the name of Nigel W. Meek, et al. and U.S. Pat. No. 5,172,539, issued Dec. 22, 1992 in the name of Richard E. Jennings, et al., show examples of pull-type harvesting implements having a pivotal tongue and a mechanical drive system for providing operative power to conventional cutting and conditioning components mounted on a frame. In the implement shown in U.S. Pat. No. 4,187,664, the tongue pivots about a vertical axis located at the left side of the implement and the mechanical drive system employs a telescopic shaft coupled to a gear box located on the left side of the implement but forward of the tongue pivot axis. In U.S. Pat. No. 5,172,539, an implement is shown wherein the vertical axis about which the tongue pivots is centrally located along the frame and the gear box, also centrally located, is located forwardly of the tongue pivot axis. Among other things, a centrally located tongue permits operation of the implement on both sides of the tractor, as well as superior maneuverability for steering around obstacles and cutting square corners.
Other examples of prior art pull-type harvesting implements with centrally located pivot tongues and mechanical drive systems with centrally located gear boxes are shown in U.S. Pat. No. 4,899,523, issued Feb. 13, 1990 to Johnny Frumholtz et al., and U.S. Pat. No. 4,719,742, issued Jan. 19, 1988 to Ermacora, et al. In both of these patents, the drive shaft for mechanically driving the gear box is disposed within the tongue.
Another pull-type harvester configuration of the same general nature as those discussed above is the pivot tongue windrower shown in U.S. Pat. No. 5,272,859, issued on Dec. 28, 1993 in the name of Martin E. Pruitt, et al. This patent discloses a central gearbox mounted on the header such that the gearbox is movable relative to the implement frame. The gearbox is rotatable about a vertical axis so that the input shaft into the gearbox can generally follow the pivotal movement of the tongue, which pivots about a rearwardly located vertical axis. This type of pivotal gearbox eliminates the occurrence of sharp angles in universal joints in the mechanical drive line connected to the gear box under conditions where the tongue swings between its extreme angular positions.
To accomplish the coordinated movement of the rotation of the gearbox with the pivotal movement of the tongue, U.S. Pat. No. 5,272,859 discloses a telescoping steering mechanism that interconnects the tongue and the gearbox such that the gearbox is rotated in response to the pivoting movement of the tongue relative to the implement frame. The telescopic action of the steering mechanism is operable to accommodate the changes in distance of the respective connecting points of the telescoping mechanism between the tongue and the gearbox, i.e., as the tongue pivots from side to side, the distance between the different horizontally spaced pivot axes of the tongue and gearbox changes. The telescopic action of the steering mechanism, along with a horizontal pivot or a ball joint, also allows the steering mechanism to follow the vertical movement of the header relative to the tongue without restricting movement of the header or the tongue.
A telescopic steering mechanism, such as taught by U.S. Pat. No. 5,272,859, suffers from operational problems associated with vibration due to the telescopic parts, which by necessity are loosely fitting, and become more so due to wear of the sliding parts. The implement, as can be seen in the drawings of U.S. Pat. No. 5,272,859, can be provided with a rotatable cutting mechanism and a crop conditioning mechanism, which are typical of hay harvesting components. The operation of rotating harvesting components, such as these, provides a substantial amount of vibration within the implement. Since the steering mechanism is loosely constructed to permit the necessary relative pivotal movements of the header and the tongue, operational vibrations are not uncommon. These vibrations lead to noise and wear in other elements and parts of the harvester. Furthermore, the looseness of the elements and the sliding action therebetween also cause substantial wear in the steering mechanism itself, resulting in increased likelihood of malfunction, or even worse, failure leading to costly downtime.
Additionally, the mechanism of U.S. Pat. No. 5,272,859 is subject to side forces from the torque applied to the gearbox by the drive mechanism and the cutterbar forces within the crop harvesting header on which the rotatable gearbox is mounted. These external forces place a side load on the steering mechanism linkage and can result in a binding of the telescoping tubes forming the linkage, which results in a thrust load on the gearbox and the connecting apparatus, particularly when the header rises and the telescopic tubes slide together. These telescoping tubes also present a hinge-like degree of freedom which can contribute further to vibrations in the instrument.
Accordingly, an important object of the present invention is to provide a crop harvesting implement that overcomes the above mentioned problems encountered in the prior art.
It is another object of the present invention to provide a steering mechanism cooperable with the mechanical drive line.
It is a feature of the present invention that the drive line supported by the tongue to deliver rotational power to the gearbox is retained in substantial alignment with the tongue.
It is yet another object of the present invention to provide a steering mechanism that generally maintains alignment of the gearbox input shaft with the tongue as its tongue pivots about the tongue pivot axis during field operation.
It is another feature of the present invention that the steering mechanism minimizes the operating angles of the universal joints in the mechanical drive line.
It is an advantage of the present invention that the steering mechanism can be easily removed and stored for lateral transport of the implement.
It is another advantage of the present invention that the universal joints in the drive line supported by the tongue of a pull-type harvester are subjected to minimal deflection.
It is a further advantage of the present invention that the life of the drive line is increased.
It is another advantage of the present invention that the steering mechanism is connected at the rear of the tongue by plates so that if the pivots wear, only the plates need to be replaced.
It is another feature of the present invention to provide a steering mechanism that is durable in construction, inexpensive of manufacture, ease of maintenance and facile in assemblage.
These and other objects, features, and advantages are accomplished according to the present invention by providing a crop harvesting implement having a wheeled frame, a draft tongue pivotable between extreme left and right operating positions, a mechanism for pivoting the tongue, a drive line for transmitting rotational power from a tractor when coupled thereto, a crop harvesting header suspended from the frame and having operable components for engaging and processing crop material, a gearbox for receiving rotational power from the drive line and transmitting the power to the operable components of the crop harvesting header, an input shaft operatively connected to the drive line, a means for mounting the gearbox on the header so that the header rotates, and a steering mechanism for effecting rotational movement of the gearbox in concert with the pivotal movement of the tongue. The steering mechanism is located on the drive line to pivot the gearbox about its generally vertical pivot axis in response to the pivotal movement of the tongue during field operations so as to keep the input shaft of the gearbox at least generally aligned with the tongue.
The foregoing and other objects, features, and advantages of the invention will appear more fully hereinafter from a consideration of the detailed description that follows, in conjunction with the accompanying sheets of drawings. It is to be expressly understood, however, that the drawings are for illustrative purposes and are not to be construed as defining the limits of the invention.